SPOILER: This article is a review of the 50th anniversary episode of Doctor Who entitled The Day of the Doctor.
After some 800 episodes, produced under the watch of more than a dozen show-runners with very different visions for the show, Doctor Who has slowly, carefully and not always neatly built a universe as vast and complex as our own.
Sonic screwdrivers, TARDIS keys, recorders, sticks of celery, Fez hats, Daleks, dematerialisation circuits, Zygons and cloister bells have been knitted into a rich and detailed tapestry. So, how do you mark an anniversary in a fashion that pays tribute to it all?
In that sense, the 50th anniversary episode of Doctor Who - titled The Day of the Doctor - faces an impossible task.
Just as every Doctor is different, every fan's perspective is shaped by the era of the show with which they feel the closest association, from actor William Hartnell in 1963 to the present day.
But out of that tornado of detail comes an hour of television as crisp and powerful as any the series has delivered. And it has delivered some greats, from 1967's Tomb of the Cybermen to 1975's The Pyramids of Mars, from 1977's Talons of Weng-Chiang to 2007's Blink.
In an historical sense, this is an episode which is steeped in Doctor Who's own history. It sees The (11th) Doctor (Matt Smith) cross paths with The (10th) Doctor (David Tennant) and another Doctor, the mysterious War Doctor (John Hurt).
In a mini-episode released online by the BBC last week, we glimpsed this nether-doctor, created when an ancient female sect connected to the Time Lords offered a dying Doctor (Paul McGann, reprising the role of the 8th Doctor) a chance to save his people, enmeshed in a war of attrition with the Daleks, by regenerating into a "warrior".
That conflict - The Time War - has been heavily referenced in the lore of modern-era (post-2005) Doctor Who, as a momentous clash of two old enemies which ended only when The Doctor - now revealed to be Hurt - destroyed both sides to save the universe.
This episode takes us into the heart of the battle and finally brings to the screen situations and icons referenced in the series but never before seen: The Fall of Arcadia, a city on the Time Lord home planet Gallifrey, and The Moment, a devastating weapon of war equipped with a living conscience.
The episode effectively brings together three doctors - Smith's, Tennant's and Hurt's - a tradition first established for the show's anniversaries with the 1973 serial The Three Doctors, which brought the Doctors played by William Hartnell, Patrick Troughton and Jon Pertwee together to save the Time Lords.
"I think there's three of them now," quips one character in this episode.
"There is a precedent for that," replies Kate Stewart, the on-screen daughter of the show's iconic Brigadier Gordon Alistair Lethbridge Stewart, who works for the same organisation as her father: UNIT, originally the United Nations Intelligence Taskforce, later the Unified Intelligence Taskforce. (The Brigadier was played by actor Nicholas Courtney, who died in 2011.)
There are nods aplenty to the various times and faces of The Doctor: the episode opens with the show's original 1963 title sequence, there is an appearance by past companion Rose Tyler (Billie Piper), albeit in the form of "Bad Wolf", her time-vortex-fuelled self which The Moment uses to articulate its conscience and, lovingly, a cameo by Tom Baker's iconic scarf.
What follows, however, is not a Shakespearean tragedy set in a pivotal moment in the history of Doctor Who, but rather an opportunity for the show's producer Steven Moffat to re-align the universe which he inherited from writer/producer Russell T. Davies, who steered the reboot of the series in 2005.
Davies' vision was the Doctor as a solitary warrior, alone in the universe, with both Daleks and Time Lords wiped from history's bloodiest page by his own hand.
Wiping the Time Lords from history was a bold call by Davies, but one which gave the series a much-needed darkness, a tone which both Davies and Moffat have exploited in their writing to devastating effect.
The Day of the Doctor, however, delivers the Doctor a second chance, to save the universe - or at least the Time Lords - from doom. Rather like the Time Lord trick of locking away the soul in a fob watch, a more picturesque gimmick is chosen here, but one which clearly puts the Time Lords back on the table in Moffat's universe. Or at least a waves tendril of hope in that direction.
There are laughs, and a little tear, and indeed one of those very uplifting Doctor Who moments when all 13 incarnations of The Doctor team up to pull off a plan hatched (as they all are) on a mad whim.
Given three of the actors are deceased, that moment requires a little digital trickery, but to see glimpses of William Hartnell, Patrick Troughton, Jon Pertwee, Tom Baker, Peter Davison, Colin Baker, Sylvester McCoy, Paul McGann and Christoper Eccleston working alongside Smith and Tennant (and Hurt) is, for a fan, truly magical.
Even the future Doctor, actor Peter Capaldi, who takes over the role at Christmas, is glimpsed. And with a McGann-Hurt regeneration seen in the mini-episode The Night of the Doctor, and a Hurt-Eccleston regeneration glimpsed in this, Moffat has completed a most unusual mosaic: the regenerations of every doctor into the next have now been seen, in some way, on screen.
The beauty of Doctor Who is that just when you think it can't get more magical (or ridiculous) it does. And Day of the Doctor ends with a cameo appearance to end all cameo appearances, that of the show's most iconic Doctor, his fourth incarnation, played by actor Tom Baker.
It's a gentle conversation, between Smith's Doctor and Baker's Doctor, shrouded in the kind of ambiguity that makes Doctor Who the best kind of jigsaw puzzle to play with.
"If I were you," muses Baker's Doctor, as he and Smith's Doctor sit contemplating a three-dimensional painting of a war-scarred Gallifrey.
"Perhaps I was you, of course. Or perhaps you are me," he continues.
"Or perhaps it doesn't matter either way. Who knows."
Who knows, indeed. Is it a question? Or a statement? Or both?
In some respects, the 50th anniversary of Doctor Who is something of a misnomer.
The series was axed midway through its life by the BBC, for whom it has lately become a jewel in the crown, the net result of which is that it has actually only been on air for some 36 of those 50 years.
And yet in those 36 years we have seen 11 Doctors Who, with glimpses of others, rival Time Lords like The Master, The Rani and The Meddling Monk, monsters such as the Daleks, Cybermen and Zygons, companions from Ian, Susan and Barbara, to Sarah Jane Smith, and Rose Tyler and the magnificently ordinary Donna Noble. (Fastest temp in Chiswick, if you recall.)
But the heart of the series, and its astonishing success, is very simple.
"Stuck between a girl and a box. Story of your life," quips Rose Tyler in one scene.
And there it is, why all of this works: Doctor Who is an idea built on the childhood fantasy of running away to see the world, save the world and get the girl (or the boy). It is a dream as universal as time and space itself.
The Day of the Doctor delivers as pure escapist fun, with silly moments, over the top performances and lots of things that go ding. (Not to mention one handy big red button.)
But it also delivers with heart. Two of them, in fact, just as you might expect. And a lot of soul.
It was once said that "a classic is a book that has never finished saying what it has to say."
In that sense, Doctor Who is indeed a classic. And Day of the Doctor an instant classic among many on it shelves.
- Sydney Morning Herald